Teak Case Study

2.1 Improved plant material for establishing successful teak plantations

For planting, teak vegetative material comes from seeds or vegetative propagation (clones). Careless selection of plant material is one of the main causes of plantation failure. There has been considerable progress in producing improved seed from seed areas and orchards, increasing the overall quality of plants used for many projects. To obtain considerable genetic gains in shorter time clonal propagation has shown to be an excellent option. Clonal seedlings from very exceptional trees are gaining acceptance (Goh & Monteuuis, 2015). Several institutions around the world (Table 1) are producing excellent quality clonal material in large amounts thanks to new propagation
The concept of site includes the set of biotic and abiotic factors that influence tree growth. Teak is native to regions of South Asia with a monsoon climate. It develops on fertile soils of alluvial, limestone, and basalt origin (Kaosa-ard., 1989). Teak has been planted in a large variety of site conditions inside and outside of its native area across the tropics, including extremes of climate and soil conditions. Complex relationships between climate and soils (soil evolution depends on parent material and climate) and specific requirements of teak combine so that optimal growth is limited to relatively small areas. E.g., in dry climates teak can be grown, but if soils have little water holding capacity, prospects of a successful plantation are reduced. Moreover, teak requirements appear to vary according to genotype and site as reported in Central America, Brazil, and Africa (Alvarado, 2013; Matricardi, 2013; Dreschel & Zech, 1994). Careless assessment of site conditions can lead to plantation failure or poor growth. On the other hand, the feeling that it is possible to reach higher yields in shorter time highlights the need of precise assessment of site characteristics that favor (or limit) optimal growth with minimum risks. Table 2 resumes the ranges of site factors allowing acceptable to optimal teak growth, and growth/survival limiting values of such
Some operations are general for all sites, whereas, others are specific to special site/genotype conditions. Adequate soil preparation must be realized to provide optimum physical soil conditions, improve water holding capacity, and enhance nutrient availability for optimum root growth. Soil preparation goes from minimum tillage systems to methods that imply the modification of some soil properties through mechanical, chemical, and biological procedures (Figure 3). Soil tillage is often used to reduce soil compaction and improve superficial drainage. Tillage includes activities such as ploughing, disking, ripping, and subsoiling. The latter is used to break hard horizon layers and to improve the structure of clayed soils. Bedding consisting in making mounds improves drainage in soils that show minor excess water problems, such as small flooding during very short periods. In Venezuela, bedding is a common practice to avoid effect of short flooding at initial plantation stages. Besides it provides an increased volume of low bulk density, aerated soil. However, if along the growth season, the soil water table is close to the surface, future growth will be poor. In México complex drainage systems have been built to avoid soil flooding produced by periodical river inundations. If soils are very acidic, liming and fertilization can be used as amendments (Section